Partial-range tracking indicator

ABSTRACT

A first mechanical system monitors the total displacement of an element within an input device. A second mechanical system monitors only a critical increment of that displacement. The first system activates and deactivates the second system at the boundary of the critical increment. The second system operates an electromechanical readout transducer. In this way the readout resolution of the transducer is increased for the displacement increment of critical concern.

United States Patent [72] Inventors Harold 0. Wires;

Samuel E. Richly, both at Columbus, Ohio 1211 Appl. No 825,349 [22]Filed May 16.1969 [45] Patented July 13, 1971 I73] Assignee The UnitedStates of America as represented by the Secretary oi the Interior [54]PARTIAL-RANGE TRACKING INDICATOR 7 Claims, 3 Drawing Figs.

116/124,:540/282 s11 lnt.C1 Gld5/04 so FieldotSearch 340 117,

[561 References Cited UNlTED STATES PATENTS 1,234,021 7/1917 Harringtonet a1 H 116/124 2.891.239 6/1959 Parsons 340/177 3,405,388 /1968 Byrne340/282 Primary ExaminerJohn W. Caldwell 1 Assistant Examiner-R. .1.Mooney Attorneys-Ernest S. Cohen and Gersten Sadowsky 82 READOUTeorsunouersn DEVICE 56 56 5a m 3 e4 6 2 0 34 Q 3o 38 66 2: 36 -7 1 4a )8i P20 I 1 1 ,5 ,L-l

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sum 2 OF 2 HAROLD 0. WIRES SAMUEL 1 RIC/(LY ATTORN PARTIAL-RANGETRACKING INDICATOR BACKGROUND OF THE INVENTION This invention generallyconcerns tracking indicators, and more particularly a tracking indicatorwhich transduces the displacement of an element into representativeelectrical signal for only a selected part, or fraction, ofa largertotal displacement oT the element, while at the same time mechanicallymonitoring the total displacement.

in monitoring the displacement of an element, a small increment of thedisplacement is often of critical concern, while the remainingdisplacement is of lesser consequence. For example, when graphicallyrecording the opening and closing of a gate in a darn, the initialincrement of displacement of the gate yields the most importantdisplacement information. When the entire range of opening of the gateis recorded, the resolution of the initial increment is decreasedbecause the largest part of the available space on the graph is taken upby unnecessary displacement infomia ion. By recording only thedisplacement increment of critical concern, the entire width of thegraph is used for that increment, and the readout resolution for theincrement increased appreciably.

When a selected increment of a total larger displacement of a dam gateis recorded, the accuracy of the record depends upon a precisedetermination of the entry into, and exit from that increment by thegate. Otherwise the boundaries of the increment are not accuratelydetermined, and the record is ambiguous. In order to precisely determinethe boundary of the increment as the gate is first opened and thenclosed, the entire range of displacement is monitored in addition to thepartial range. Then, as the gate enters into and exits from the selectedincrement a recorder is activated or deactivated, respectively.

SUMMARY OF THE INVENTION This invention is a partial range trackingindicator for monitoring a selected increment out of a larger totaldisplacement of an element. In the tracking indicator a threaded collaris transtated along a threaded rod by rotating the collar in pro portionto the displacement of an element in an input device. The position ofthe collar upon the rod represents the displacement position of theelement in the input device.

A transition gear is biased by one coil spring for translation with thecollar along the threaded rod, and is driven by another coil spring forrotation along with the threaded collar. The rotation of the transitiongear operates an electromechanical transducer which converts themechanical displacement of the gear into an electrical analogue signalfor operating a readout device. The rotation of the transition gear isproportional to the displacement of the element in the input device, andthe electrical analogue signal represents the displacement of theelement.

At a predetermined point, which point is at the boundary of theincrement of critical concern in the translation of the collar andtransition gear along the threaded rod, the transition gear encounters arigid stop and ceases rotating and translating with the threaded collar.The operation of the electromechanical transducer by the transition gearsimilarly ceases. The threaded collar continues to rotate for monitoringthe total displacement of the element in the input device.

When the displacement of the element in the input device reversesdirection, the translation of the threaded collar similarly reversesdirection As the displacement of the element enters the increment ofconcern, the collar contacts the transition gear at he rigid stop androtates the gear against the force ofthe coil spring, again operatingthe electromechanical transducer. in this the incremental readout issynchronized with the total displacement or the element.

Therefore, it is an object of this invention to provide a trackingdevice for monitoring the total displacement of an element.

A further object of this invention is to provide a tracking device formonitoring the total range of displacement of an element, and forproviding a readout indication for a partial range of the totaldisplacement.

A further object of this invention is to provide a partial rangetracking indicator which establishes the boundary between a total and apartial range of displacement with repetitive accuracy.

These and other objects of this invention will become more fullyapparent with reference to the following specification and drawing whichdescribe the preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a plan view ofa partial rangetracking indicator.

FIG. 2 is a side view of the partial range tracking indicator shown inFIG. 1.

FIG. 3 is a side view ofthreaded collar and a transition gear shown inFIGS. I and 2, viewed along section lines 3-3 in FIG. I.

DETAILED DESCRIPTION OF THE INVENTION In FIG. I an input device 2 isoperatively connected through a mechanical linkage 4 to a driving gear6, which rotates on a shaft 8. The input device 2 may be any device inwhich an ele ment is operable over a range of positions, whether byrotational or translational displacement. As displacement of the elementwithin the input device occurs, a proportional displacement stimulus isfed from the element, through the linkage 4 and gear 6, to a partialrange tracking indicator Ill. The tracking indicator I0, shown in FIGS.1 and 2, monitors the displacement of the element within the inputdevice 2, and provides an indication of a partial increment of thatdisplacement. Once the partial increment of displacement is exceeded,the output indication of the tracking indicator I0 remains at a presetmaximum, representative of that partial increment. When the displacementdirection of the element within the input device 2 reverses, and theelement returns toward its original position, the tracking indicationagain represents the actual position as the element passes the presetmaximum indication position in the return path.

By discriminatively indicating only the partial increment of criticalconcern in the total displacement of the element in the input device 2,the partial range tracking indicator increases the readout resolutionfor that critical increment. The tracking indicator I0 employs anelectromechanical transducer 68 which converts displacement informationinto an electrical analogue signal for operation of a recorder, orsimilar readout device 78.

The range of the transducer 68 is I'fiSII'ICtuLI by the physicallimitations inherent in its construction. For measurement ofa range ofdisplacement, the transducer is driven between limit stops. As thelimits upon the total measured displacement of the element in the inputdevice 2 are increased, the fractional displacement of the transducerfor each increment of that total displacement is decreased.Consequently, the resolution of the transducer 68 is inverselyproportional to the total displacement measured. To avoid this decreasein resolution where the element traverses a large displacement, anincrement of critical concern is selected in the total range ofdisplacement, and the transducer is driven between its limits for thatincrement. In the tracking indicator shown in FIGS. I-3, the incrementselected for readout indication is the initial increment of displacementof the element. In addition, to insure repetitive activation anddeactivation of the transducer at the precise boundary of the increment,the partial range tracking indicator 10 also monitors the entire rangeof displacement.

Referring to FIG. I, the displacement of an element input device 2 isconverted by a linkage 4 and a driving gear 6 to a rotationaldisplacement of a double input gear 12 in the tracking indicator I0. Theinput gear I2 has parallel rows of teeth I4 and 16 which rotate inunison with a hollow shaft I8.

The hollow shaft 18 is supported for rotation and translation withinbearings 20 on pillow blocks 22. A fastener 24 on gear 12 rides freelywithin a key way 26 which extends longitudinally on the shaft I8 betweeneach end of the shaft. The fastener 24 effectively couples the gear 12to the hollow shaft 18 for simultaneous rotation of the gear and shaft,while permitting lateral displacement of the shaft within the gear. Oneset of gear teeth l4 engages the input gear 6 for rotating the shaft I8,while the other set engages another gear 27 for driving a digitalrotation counter 28.

An internally threaded collar 30 is fixed concentrically to one end ofthe hollow shaft [8, and one end ofa threaded rod 32 is threaded withinthe collar. The other end of the threaded rod 32 is fastened to a pillowblock 34 by a pair of nuts 36, so that the rod is rigidly fixed inconcentric alignment with the hollow shaft 18. As the hollow shaft 18 isrotated in a counter clockwise direction by input gear 12, (viewed fromthe collar end of the shaft), threaded collar 30 rotates, and the screwthreads on collar 30 and rod 32 draw the collar and shaft along the rodin the direction to the fixed end of the rod. As the shaft l8 translatesalong the rod 32, the rod extends into the hollow space within theshaft. When the hollow shaft [8 is rotated in a clockwise direction, theshaft translates away from the fixed end of the rod.

The position of the threaded collar 30 upon the rod 32 is directlyrelated to the amount of rotation of input gear [2. Similarly, theamount of rotation of the input gear 12 is directly related to thedisplacement of the element in input device 2. Therefore, the positionof the collar 30 on the rod 32, with respect to a fixed datum, isdirectly related to the total displacement of the element in the inputdevice. The collar 30 follows the displacement of the element in theinput device for monitoring the exit from, and entry of the elementinto, the increment of critical concern.

A smooth bored transition gear 38 rotates and translates freely upon theshaft 18 adjacent to threaded collar 30. The transition gear 38 isbiased in the direction of the collar by a coil spring 40 which extendsbetween a pair of washers 42 on the shaft. A narrow detent bar 44, fixedto the gear 38, extends radially beyond the periphery of a collar 46 onone end of the gear 38, as best seen in FIGS. 2 and 3. The detent bar 44cooperates with an adjustable detent 48, which extends through thecollar 30 in the direction of the shaft 18, to synchronize the rotationof collar 30 with the rotation of the gear 38.

The detent 44 on the transition gear 38 is rotationally biased againstthe detent 48 on the collar 30 by the torque of a coil spring 50. Thetorque from spring 50 is transmitted to gear 38 and detent 44 through atrain of gears. The constant torque spring 50 is wound in an S-shapedspiral on spools $2 and 54 which are mounted for rotation on pillowblocks 56. The spring 50 is secured at each end to a spool and tends torewind onto spool 54. The spring supplies a constant counterclockwisetorque (viewed from left to right in FIGS. 1 and 2) at an output gear58. This torque is transmitted by a gear to an elongated gear 62 whichis mounted for rotation with a common shaft 64 between pillow blocks 66.The elongated gear 62 transmits a constant counterclockwise rotationaltorque to the transition gear 38, biasing the fixed detent 44 in acounterclockwise direction against the adjustable detent 48. When thecollar 30 rotates in a counterclockwise direction, the transition gear38 follows the rotation of the collar as the spring 50 rewinds ontospool 54. When the collar 30 rotates in a clockwise direction, thecollar drives the transition gear 38 against the force of spring 50, andthe spring 50 is wound onto spool 52.

The position of collar 30 along the threaded rod 32 representsdisplacement of the element within the input device 2. Since thetransition gear 38 follows the collar 30, the position of the gear alsorepresents displacement of the element. ln addition, the amount ofrotation of transition gear 38 is directly proportional to, andrepresentative of the displacement of the element in the input device.In view of this rotational proportionality, the transition gear isemployed to control an electromechanical potentiometer 68 for convertingthe displacement information transmitted by the gear 38 into anelectrical analogue signal. Rotational displacement information istransferred from transition gear 38 to the potentiometer 68 through theelongated gear 62, a sprocket 70 on shaft 64, a positive drive belt 72,and a second sprocket 74 on input shaft 76 of the potentiometer. Theoutput from the potentiometer is fed to a readout device 78, which maybe a graphical recorder, for example, for permanently recording thedisplacement of the element within the input device. The potentiometerand readout device are each supported on a suitable base 80.

A digital-rotation counter 81 is used to visually monitor thedisplacement input to the potentiometer 68. A gear 82 on thepotentiometer shaft 76 engages a second gear 84 on the shaft of thecounter 8|, driving the counter whenever the potentiometer is driven.The ration of the gears driving the counter 8| is designed tosynchronize the reading on the counter 8l with the reading on the othercounter 28 for a given displacement input.

As increasing displacement of the element in input device 2 occurs, thecollar 30 and transition gear 38 translate together along the threadedrod 32, while rotating in a counterclockwise direction. Simultaneously,the transition gear feeds displacement information to the potentiometer68. When a preselected increment of displacement has occurred, thetransition gear 38 reaches a stop 86 which blocks further translation ofthe gear 38 along the rod 32. The detent bar 44 on the gear 38 strikes aside 88 of the stop 86 (as best seen in F l6. 3) preventing furtherrotation of the gear. The collar 30 then continues to rotate, advancingalong the threaded rod 32. The pitch of the threaded rod 32 and theprotrusion of the fixed detent bar 44 and adjustable detent screw 48 arechosen so that a single revolution advances collar 30, with adjustabledetent 48, a distance sufficient to prevent further interference betweenthe fixed and adjustable detents 44 and 48. The relatively movablecollar 30 and transition gear 38, in cooperation with the stop 86, actas a clutch at the transition point between the incremental displacementof critical concern and the additional displacement within the inputdevice. When the face of gear 38 strikes the stop 86 the smooth boredgear rides freely on shaft 18. Further displacement of the potentiometer68 ceases, and the indication from readout device 78 shows only that thedisplacement has exceeded the increment of critical concern. At thispoint, the torque transmitted to transition gear 38 from spring 50 holdsthe detent 44 against the side 88 of stop 86, preventing fluctuation ofthe readout indication.

As the displacement of the element within the input device decreases,the collar rotates in a clockwise direction, engaging the transitiongear 38 as the stop 86 is reached. Displacement information is againtransmitted to the potelhiometcn and the readout indication againrepresents the displacement within the input device 2. Thesynchronization of the transition of gear 38 from rest to rotation atthe increment boundary is evidenced by comparing the readings of therotation counters 28 and 8]. The backlash in the gear train of thetransition indicator 10 is held to a minimum, so that when the indicatoris operating properly, the readings of the counters 28 and 81 arerepetitively coincident below stop 86.

Since a displacement input beyond the physical capabilities of thepartial range tracking indicator [0 would damage the component parts ofthe indicator, an electrical interlock with the input device 2 isprovided. Limit switches 90 and 92, at the respective upper and lowerlimits of travel of collar 30, deactivate the power circuit of the inputdevice when the collar engages linkages 94 and 96. Alternatively,switches 90 and 92 could be positioned along the path of collar 30 toactuate diverse controls as a function of displacement of the elementwithin the input device.

In adapting the present exemplary disclosure to a particular trackingenvironment other modifications within the scope of the invention willbecome apparent to those skilled in the art in the light of the aboveteachings and within the scope of the appended claims.

What we claim is:

l. A partial range tracking indicator comprising:

first means responsive to the total range of displacement of an elementin an input device for representing displacement in proportion to thetotal displacement of the element,

an electromechanical transducer,

second means responsive to a partial range of the total range ofdisplacement of the element for operating the electromechanicaltransducer within the partial range.

the first means being releasably coupled to the second means fordependent operation in the partial range of displacement, andindependent operation outside of the partial range of displacement, and

third means for uncoupling and coupling the first and second means asthe partial range is exceeded and entered, respectively.

2. An apparatus as claimed in claim I in which:

the first means includes a threaded collar mounted for rotation andtranslation on a threaded shaft,

the second means includes a smooth bored gear mounted for rotation andtranslation upon a shaft which is secured to the threaded collar, and

the third means includes a detent on the threaded collar, a detent onthe smooth bored gear, and a rigid stop which is fixed relative to themovement of the collar and the gear.

3. The apparatus as claimed in claim 2 in which:

the electromechanical transducer is driven by a source of motive powerindependent of the element and the smooth bored gear operates thetransducer by regulating the transmission of motive power from thesource to the transducer.

4. The apparatus as claimed in claim 3 in which:

the source of motive power includes a coil spring.

5. The apparatus as claimed in claim 1 in which the electromechanicaltransducer is electrically connected to a readout indicator.

6. The apparatus claimed in claim 2 in which the electromechanicaltransducer is electrically connected to a readout indicator.

7. The apparatus as claimed in claim 4 in which the electromechanicaltransducer is electrically connected to a graphical recorder.

1. A partial range tracking indicator comprising: first means responsiveto the total range of displacement of an element in an input device forrepresenting displacement in proportion to the total displacement of theelement, an electromechanical transducer, second means responsive to apartial range of the total range of displacement of the element foroperating the electromechanical transducer within the partial range, thefirst means being releasably coupled to the second means for dependentoperation in the partial range of displacement, and independentoperation outside of the partial range of displacement, and third meansfor uncoupling and coupling the first and second means as the partialrange is exceeded and entered, respectively.
 2. An apparatus as claimedin claim 1 in which: the first means includes a threaded collar mountedfor rotation and translation on a threaded shaft, the second meansincludes a smooth bored gear mounted for rotation and translation upon ashaft which is secured to the threaded collar, and the third meansincludes a detent on the threaded collar, a detent on the smooth boredgear, and a rigid stop which is fixed relative to the movement of thecollar and the gear.
 3. The apparatus as claimed in claim 2 in which:the electromechanical transducer is driven by a source of motive powerindependent of the element, and the smooth bored gear operates thetransducer by regulating the transmission of motive power from thesource to the transducer.
 4. The apparatus as claimed in claim 3 inwhich: the source of motive power includes a coil spring.
 5. Theapparatus as claimed in claim 1 in which the electromechanicaltransducer is electrically connected to a readout indicator.
 6. Theapparatus claimed in claim 2 in which the electromechanical transduceris electrically connected to a readout indicator.
 7. The apparatus asclaimed in claim 4 in which the electromechanical transducer iselectrically connected to a graphical recorder.